QStateMachine: fix ignore high-priority events.

When a high-priority event is posted in overrided
'QStateMachine::beginSelectTransitions', the event may be remained in
event queue, and be not dispatched until another event posted.

Change-Id: Ifda288d9c00ac7985e426b9cc02bda382ebaac35
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

2 files changed, 35 insertions, 4 deletions

diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index e5d019dc8b..ee522218ee 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -1946,12 +1946,14 @@ void QStateMachinePrivate::_q_process()
                 }
         }
         if (enabledTransitions.isEmpty()) {
-            processing = false;
-            stopProcessingReason = EventQueueEmpty;
-            noMicrostep();
+            if (isInternalEventQueueEmpty()) {
+                processing = false;
+                stopProcessingReason = EventQueueEmpty;
+                noMicrostep();
 #ifdef QSTATEMACHINE_DEBUG
-            qDebug() << q << ": no transitions enabled";
+                qDebug() << q << ": no transitions enabled";
 #endif
+            }
         } else {
             didChange = true;
             q->beginMicrostep(e);
diff --git a/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp b/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp
index 1292c3b98f..e60b1c983c 100644
--- a/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp
+++ b/tests/auto/corelib/statemachine/qstatemachine/tst_qstatemachine.cpp
@@ -250,6 +250,7 @@ private slots:
     void internalTransition();
     void conflictingTransition();
     void qtbug_46059();
+    void postEventFromBeginSelectTransitions();
 };
 
 class TestState : public QState
@@ -6485,5 +6486,33 @@ void tst_QStateMachine::qtbug_46059()
     QVERIFY(machine.isRunning());
 }
 
+void tst_QStateMachine::postEventFromBeginSelectTransitions()
+{
+    class StateMachine : public QStateMachine {
+    protected:
+        void beginSelectTransitions(QEvent* e) Q_DECL_OVERRIDE {
+            if (e->type() == QEvent::Type(QEvent::User + 2))
+                postEvent(new QEvent(QEvent::Type(QEvent::User + 1)), QStateMachine::HighPriority);
+        }
+    } machine;
+    QState a(&machine);
+    QState success(&machine);
+
+    machine.setInitialState(&a);
+    a.addTransition(new EventTransition(QEvent::Type(QEvent::User + 1), &success));
+
+    machine.start();
+
+    QTRY_COMPARE(machine.configuration().contains(&a), true);
+    QTRY_COMPARE(machine.configuration().contains(&success), false);
+
+    machine.postEvent(new QEvent(QEvent::Type(QEvent::User + 2)), QStateMachine::NormalPriority);
+
+    QTRY_COMPARE(machine.configuration().contains(&a), false);
+    QTRY_COMPARE(machine.configuration().contains(&success), true);
+
+    QVERIFY(machine.isRunning());
+}
+
 QTEST_MAIN(tst_QStateMachine)
 #include "tst_qstatemachine.moc"